Investigation on Steelmaking with Hot Metal Containing Low Silicon Content in Large Converter

There are some problems in steelmaking with hot metal containing low silicon content such as difficulty in slag formation, less slag for dephosphorization and slag adhesion on oxygen lance and hood. To overcome these problems, experiments wcrc conducted and some improvements were obtained, such as adding appropriate flux, increasing the lance position slightly during steelmaking and using effective multi-outlet nozzle. Moreover, to keep normal heating rate, the ore and scrap charge should be reduced due to less chemical heat input in steelmaking.

Primary slag formation behavior during reduction process of SFCA-I and SFCA

Because the formation behavior of primary slag which decomposed from complex calcium ferrite(SFCA-I and SFCA)is not quite clear,the migration behavior of CaO and Al_(2)O_(3) derived from high basicity or high alumina sinter is always worth studying.The reducibility of three representative sinter samples and the formation behavior of primary slag during reduction process were investigated via X-ray diffraction,scanning electron microscopy,and energy-dispersive spectroscopy characterization.The results show that the reducibility of high basicity sinter is superior to that of high alumina sinter.Minerals with poor reducibility like hercynite and brownmillerite and with large-grained particles like free alumina and silica form in sinters with basicity of 2.4 and Al_(2)O_(3) content of 4 wt.%,respectively.The appearance of these minerals can well explain the reduction stagnation phenomenon occurring in these sinter samples.The migration behavior of CaO and Al_(2)O_(3) during slag formation process is different.CaO can easily combine with SiO2 to form silicate phase or firstly form calcium-rich ferro-aluminate solid solution and then transform to silicate phase,while Al_(2)O_(3) firstly combines with CaO and FeO to form solid solution and then,gradually combines with SiO2 to form calcium aluminum silicate phase.

Inclusion evolution in 50CrVA spring steel by optimization of refining slag

In order to control the CaO-Al;O;-SiO;-MgO system inclusions in 50 CrVA spring steel in a lower melting temperature region,high temperature equilibrium experiments between steel and slag were performed in the laboratory,under the conditions of the initial slag basicity within 3-7and the content of Al;O;between 18-35mass%,to investigate the formation and evolution of this type of inclusion.The results indicate that the total oxygen content in the steel decreases with the increase of slag basicity and the decrease of Al;O;content in slags,and CaO-Al;O;-SiO2-MgO inclusions tend to deviate from the low melting point region with the increase of Al;O;content in slags.The most favorable composition for the refining slag is composed of 51-56mass% CaO,9-13mass% SiO;,20-25mass% Al;O;and 6mass% MgO.In this case,the inclusions in 50 CrVA spring steel are mostly in the low melting point regions,in which their plasticities are expected to improve during steel rolling.The MgO-based inclusions were observed in the steel matrix and the formation mechanism was theoretically and schematically revealed.It is also found that adding around 11mass% of MgO into the refining slags is beneficial to reducing the refractory corrosion.Further work should be carried out focusing on the evolution rates of MgO-based inclusions.